Wikipedia is the most popular free encyclopedia online, and now it's available on Windows 8 as a Metro app.
Wikipedia is a user-edited website that contains literally millions of pages about virtually any subject under the sun. Now you can access the site directly through the Wikipedia Metro app to search for whatever topics suit your current whims.
The Wikipedia app's interface is just about as simple as the website itself. You can search by topic via a search bar, or else click through highlighted links in the text that you're already reading on a current subject. Wikipedia's Metro app uses the same basic color scheme as the website, meaning articles are easy to browse and read.
In addition, you can pin articles for later reading, as well as share articles to other Metro applications. Wikipedia also has support for articles in different languages.
Wikipedia has nice integration with Metro, as well as all the great information you want about any topic of your choosing.